In the recent years, with the rapid development of the electronic products, the demand for the storage mediums have increased rapidly. The rewritable non-volatile memory has characteristics such as non-volatility of data, power saving, small volume, non-mechanical structure, fast reading and writing speed, and so on. The solid state drive (SSD) is a memory storage device including a flash memory as a storage medium.
When a space of physical erasing units in an idle region is substantially occupied during the operation of the memory storage device, a storage control circuit of the memory storage device transmits valid data in at least one of the physical erasing unit in the data region to be stored in an unusable physical programmable unit of another physical erasing unit in the data region. The storage control circuit of the memory storage device then executes an erase operation on the physical erasing unit storing only invalid data and classifies the erased physical erasing unit to the idle region, such that the physical erasing units can be alternately used for storing data in response to the subsequently executed writing instruction. In order to prevent the space of the physical erasing units in the idle region from being substantially occupied, when the capacity of the physical erasing units in the idle region is reduced to be lower than a garbage collection threshold, the storage control circuit executes a data merging program such that the data in the physical erasing units become invalid data. The physical erasing unit storing only the invalid data is reclassified to the idle region. For example, when the data merging program is executed, the storage control circuit needs to use at least one empty physical erasing unit. Therefore, the garbage collection threshold needs to be larger than a minimum threshold. However, it takes a lot of time to execute the data merging program. More specifically, when the host system requires a large amount of data to be written in a short time and the space of the physical erasing units in the idle region is substantially occupied, a large amount of time is required for the storage control circuit of the memory storage device to execute the data merging program. As a result, the data cannot be written at a predetermined time and the stored data may suffer loss.
In addition, when the solid state disk synchronously executes tasks, the consumed system resources may cause the host system to have an unstable operation speed. Under normal circumstances, even if the speed of the autonomous host system temporarily drops, the program of writing the non-sequential data will not be affected. However, for a storage carrier that must execute the program of writing the sequential data, for example, playing a movie device or a digital camera, etc., the temporary slowdown of the above host system may cause the image to drop frames.
Taiwan Patent No. TW201518945A discloses that the physical erasing units of the rewritable non-volatile memory storage device are classified into the data region and the idle region. The logical units are configured to be mapped with the physical erasing units in the data region. The rewritable non-volatile memory storage device is dynamically configured to include the predetermined number of the physical erasing units dedicated for writing the sequential data. When a command sequence sent by the host system indicates that the sequential data and the random data is written to the same die in the solid state hard disk, mutual interference may occur. Accordingly, the above conventional methods of writing the data are not optimized for a large amount of the sequential data.